U.S. patent number 7,434,535 [Application Number 10/749,685] was granted by the patent office on 2008-10-14 for timing device.
This patent grant is currently assigned to Church & Dwight Co., Inc.. Invention is credited to Steven T. Adamy.
United States Patent |
7,434,535 |
Adamy |
October 14, 2008 |
Timing device
Abstract
A timing device for visually determining the passage of a
preselected period of time including a redox indicator and a metal
salt wherein the indicator undergoes an observable change in color
which is related to the desired preselected period of time.
Inventors: |
Adamy; Steven T.
(Lawrenceville, NJ) |
Assignee: |
Church & Dwight Co., Inc.
(Princeton, NJ)
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Family
ID: |
34701081 |
Appl.
No.: |
10/749,685 |
Filed: |
December 31, 2003 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050141348 A1 |
Jun 30, 2005 |
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Current U.S.
Class: |
116/206; 368/327;
374/E3.004 |
Current CPC
Class: |
G01K
3/04 (20130101); G04F 1/06 (20130101) |
Current International
Class: |
G01D
21/00 (20060101) |
Field of
Search: |
;116/206,216-219
;374/161,162,106 ;368/114,327 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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60093983 |
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May 1985 |
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JP |
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01202660 |
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Aug 1989 |
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JP |
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Primary Examiner: Smith; R. A.
Assistant Examiner: Johnson; Amy Cohen
Attorney, Agent or Firm: Frenkel & Associates Frenkel;
Stuart D. Kiefer; Phillip R.
Claims
What is claimed is:
1. A timing device for visually determining the passage of a
preselected period of time comprising: a redox couple containing a
redox indicator in combination with a reactable metal ion, said
redox couple deposed within a matrix, said matrix being exposable
to air such that over a period of time during exposure to air, the
redox indicator changes color and thereby indicates the passage of
a predetermined period of time.
2. The timing device of claim 1 wherein the matrix is a
film-forming polymer.
3. The timing device of claim 2 wherein the film-forming polymer is
a cellulose derivative.
4. The timing device of claim 2 wherein said matrix has a thickness
based on a wet film of said polymer of from 5 to 50 mil.
5. The timing device of claim 1 wherein the matrix is attached to
an adhesive tape and is adhered to a package containing a consumer
product.
6. The timing device of claim 1, wherein the redox indicator is
selected from the group consisting of indigo carmine and methylene
blue.
7. The timing device of claim 1, wherein the metal ion is
Sn.sup.2+.
8. A method for determining when a consumer product has reached an
end to its useful shelflife comprising: preparing a timing device
comprising a redox couple containing a redox indicator and a
reactable metal ion, said redox couple deposed within a matrix,
said matrix being exposable to air; attaching the timing device to
an outside surface of the consumer product; observing the timing
device for color changes, which color changes coincide with the end
of the useful shelflife of the said consumer product.
Description
FIELD OF THE INVENTION
The present invention is directed to a timing device for visually
determining the passage of a preselected period of time and is
applicable to a wide variety of consumer products, especially
products which have an extended shelf or use life and for which it
is desirable to know when the product must be replaced or
rejuvenated. The timing device can be attached to or incorporated
in typical packaging employed for consumer products.
BACKGROUND OF THE INVENTION
Consumer products including food products, cleaning products,
deodorizers and the like have a shelf life determined by the length
of time the components of the product resist change to
environmental influences. For example, food products have a given
shelf life based on their ability to resist chemical or physical
changes due to contact with air, heat and other influences in the
environment. Many consumer products are date stamped to provide the
user with an indication of the shelf life of the product. The shelf
life may be relatively short such as a few days or may be
relatively lengthy such as a few months. Date stamping of consumer
products provides the user with some indication of when the product
may no longer be useful for its intended purpose.
Quite often, date stamps are printed inconspicuously on the product
package. It is sometimes difficult to read the date stamp and in
some cases even to find the date stamp because it may be printed
anywhere on the package. Date stamping is particularly problematic
for products which have a relatively long shelf life because such
products tend to get stored in obscure recesses of a storage area,
such as a food cabinet or refrigerator. If the product is not used
often, the consumer is often unaware that the expiration date is
shortly forthcoming or has even passed.
There have been attempts to provide a visible indication of when
the useful life of a product has expired. So called life time
indicators are employed for food products such as are disclosed in
U.S. Pat. Nos. 2,671,028; 3,751,382; and 3,942,467. These
indicators typically work through chemical reactions initiated or
increased in rate by exposure to high temperatures. Other lifetime
indicators rely on diffusion of a component through a traditional
wick or membrane as disclosed in U.S. Pat. Nos. 3,414,415;
3,479,877 and 3,768,976, each of which is incorporated herein by
reference.
Examples of other such products which incorporate useful life
indicators include, for example, certain toothbrush wear indicators
which are based on the diffusion of a dye out of the bristles. When
the color of a select group of bristles disappears, the user is
aware that the toothbrush may or should be discarded and replaced.
Another example is found in a deodorizer product having a timer
based on the evaporation of a solvent from a polymer gel and
subsequent shrinkage of the gel.
The timing indicators mentioned above suffer from one or more
disadvantages which makes their universal applicability to a wide
range of packaged products problematical. Such disadvantages
include a) the timing mechanism is part of the product (e.g. a
deodorizer) and is therefore limited to employment with that
product or that class of products, b) the timing mechanism is
inaccurate or cannot be controlled to accommodate a wide range of
product shelf lives, c) the timing mechanism is expensive and/or d)
has a limited range of measurement.
U.S. Pat. No. 6,269,764 discloses a timing device which overcomes
at least some of the problems mentioned above. The device disclosed
in that patent is in the form of an inverted U-shaped tube with at
least one of the opposed ends having opposed reservoirs for storing
a reactant and an indicator with a wick employed to enable the
reactant to contact the indicator thereby initiating a color change
over a preselected period of time.
It would be an advance in the art of providing visible indicators
for determining when a product should be replaced or rejuvenated if
a cost efficient and effective shelf life indicator could be
provided which provides a clear and distinct visible indication of
when a product should be replaced or rejuvenated and does so
without employing a wicking material so as to reduce the cost of
the device.
SUMMARY OF THE INVENTION
The present invention is generally directed to a shelf life
indicator, hereinafter referred to as a timing device, for
determining the point at which a product has expired, or needs to
be changed, etc., and visually displaying the same. In addition,
the invention is directed to a timing device applicable to a wide
range of consumer products and packages containing the same. The
timing device can be applied to products which have a relatively
short shelf life (e.g. dairy products including milk) and products
which have a fairly long shelf life such as canned vegetables.
In a particular aspect of the present invention, there is provided
a timing device for determining and visually indicating the passage
of a preselected period of time. The invention is based on the
principle that certain redox indicators undergo a color change with
a change in oxidation state. A redox couple may be formed between a
redox indicator and another material, such as a metal ion.
Indigo carmine, for example, exhibits a yellow (pH 7) or colorless
(acidic pH) color in its reduced form but a blue color in its
oxidized form. As another example, neutral red exhibits no color in
its reduced form, but exhibits a red color in its oxidized
form.
The reactions set forth below demonstrate a redox couple at pH 2
between indigo carmine and Sn.sup.2+. The indigo carmine, in its
oxidized form (IC.sub.Ox), is changed to its reduced form
(IC.sub.Red) and the Sn.sup.2+ is oxidized:
IC.sub.Ox+2H.sup.++2e.sup.-.revreaction.IC.sub.Red (1a)
Sn.sup.2+.revreaction.Sn.sup.4++2e.sup.- (1b)
Following reactions 1a and 1b, the indigo carmine, in its reduced
state, is colorless or yellow, depending on the pH. According to
the present invention, the above-described reactions are carried
out in a matrix containing a film-forming polymer, such as a
cellulose derivative such as hydroxyethyl or hydroxypropyl
cellulose or mixtures thereof. In one embodiment, a polymer
solution, with the reduced indicator therein, can be drawn out into
a film and allowed to dry. In some of the examples set forth below
the film was drawn out onto glass slides for easy observation and
handling. In other examples, the firm was drawn onto an adhesive
backed polyester film which permitted the fabrication of timers
having the form of small stickers. Although the invention is not
limited to timers in the form of stickers, such stickers are a
particularly useful embodiment of the invention, as the stickers
could be applied, for example, to the surface of a consumer
product, or to the surface, either interior or exterior, of a
refrigerator, a freezer or other cabinet or container. According to
the invention, such a sticker could be constructed such that it
would undergo a color change following a pre-selected period of
time.
A film containing the reduced indicator may be exposed to air, and
over a period of time the redox indicator slowly re-oxidizes. In
the case of the indigo carmine, the indicator gradually turns from
a yellow-orange shade to a brilliant blue. The rate at which the
color change occurs depends on factors such as the ratio of redox
indicator to oxidizable metal, the particular metal salt used, film
thickness, and temperature. These are parameters which may be
selected to construct a timer which will change color after the
elapse of a pre-selected period of time, typically several days,
weeks, or months. Ratios of indicator to metal ion salt may
typically vary from about 1:30 to about 1:2. The metal ion may be
any ion able to undergo oxidation with the subsequent reduction of
an appropriate indicator. Examples of such metal ions include
Sn.sup.2+, Cu.sup.+, Fe.sup.2+, Mn.sup.2+, Pb.sup.2+, Ti.sup.n+
(n=2, 3), and Vn.sup.n+ (n=1,2,3,4). The thickness of the film may
vary with the permeability of the film-former employed, but
typically will range from about 5 to 50 mil (127 to 1270 .mu.m),
measured on the wet film. By varying these parameters a timer may
be constructed which will undergo a color change in a given number
of days at a given temperature, and that given temperature may, for
example, be freezer temperature, refrigerator temperature, ambient
temperature, or an elevated temperature.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-sectional view of the timing device of this
invention placed on an adhesive-backed film.
FIG. 2A is a depiction of the timing device of this invention
placed on a box containing a consumer good.
FIG. 2B is a depiction of the timing device of this invention
placed on a box containing a consumer good and after a period of
time indicating color change of the timing device.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the device 20 of the present invention in which a
polymer film 10, such as a polyester film containing an adhesive
layer 12 is coated with a matrix layer 14 having mixed therein a
redox indicator and a metal ion.
FIGS. 2A and 2B show a container 22 containing a consumer good in
which the timing device 20 such as shown in FIG. 1 is adhered
thereto. FIG. 2A shows timing device 20 having an initial color and
FIG. 2B shows a color change of timing device 20 upon the passage
of time and exposure to air, thus, indicating a change of freshness
of the goods within the container.
The following examples demonstrate the invention, but should not be
construed as limiting it.
EXAMPLE 1
The following composition which contains both a film former and a
redox indicator was prepared.
TABLE-US-00001 TABLE 1 Component Order of Addition Wt. % Water 1
32.84 Methanol 2 64.28 Hydroxyethyl cellulose 3 1.31 (Natrosol 250
HR CS) SnCl.sub.2.cndot.2H.sub.2O 4 1.31 Indigo Carmine 5 0.26
After initial agitation, the mixture was allowed to mix overnight
on a gently rocking platform. The mixture changed color from a deep
blue to a light teal.
A film of the composition was then drawn on a glass slide with a
controlled thickness applicator. In this case, a BYK-Gardner Square
Multiple Clearance Applicator, model PAR-S3S1, was employed to
deposit the film on the slide. The thickness of the film (wet) was
20 mil. The film was allowed to air dry overnight. The dry film
then exhibited an orange-yellow color.
The bottom half of the film area on the glass slide was wrapped in
clear plastic adhesive tape while the top half was left exposed to
air. This left an exposed area of approximate dimensions
1''.times.1''. The dry film was placed in a refrigerator at
40.degree. F. Changes in the color of the exposed top half from
orange to blue were observed.
Changing of the entire exposed area from orange to blue occurred in
45.+-.3 days.
EXAMPLE 2
The following composition was prepared.
TABLE-US-00002 TABLE 2 Component Order of Addition Wt. % Water 1
32.88 Methanol 2 64.37 Hydroxyethyl cellulose 3 1.31 (Natrosol 250
HR CS) SnCl.sub.2.cndot.2H.sub.2O 4 1.31 Indigo Carmine 5 0.13
The composition was mixed as in Example 1. A 20 mil film was also
drawn and set up for aging employing the procedure set forth in
Example 1. The color change occurred over a period of about 55.+-.6
days.
EXAMPLE 3
The film described in Example 1 was aged at room temperature
(72.+-.3.degree. F.). The size of the film was about
1/2''.times.1'', and the bottom (covered) half also went through a
color change. In this case, it appears that the barrier properties
of the adhesive tape were not sufficient to prevent oxygen exposure
at room temperature.
The color change occurred over a period of about 22 to 30 days.
EXAMPLE 4
The following composition was prepared:
TABLE-US-00003 TABLE 3 Component Order of Addition Wt. % Water 1
32.88 Methanol 2 64.37 Hydroxyethyl cellulose 3 1.31 (Natrosol 250
HR CS) SnCl.sub.2.cndot.2H.sub.2O 4 1.31 Methylene blue 5 0.13
The mixture was initially blue, but gradually turned whitish-gray.
As in Example 1, a film was drawn at a wet thickness of 20 mil.
After drying overnight, the film was placed in a refrigerator
(40.degree. F.). The bottom half of the film was wrapped in an
adhesive film while the top half of the film was exposed to the
air. The exposed half of the film underwent a color change from
white to blue over a period of about 48 days, and continued to
darken with a more intense blue up to about 95 days.
EXAMPLE 5
The compositions set forth in Table 4 were prepared. As seen
therein, the compositions contained 1:10 ratios of indigo
carmine/SnCl.sub.2.2H.sub.2O, as well as base polymers of either
hydroxyethyl cellulose (HEC, Natrosol 250 HR CS, from Hercules) or
hydroxypropyl cellulose (HPC, Klucel H CS, from Hercules), or
combinations thereof. Composition A was applied as both a 20 mil
(wet) film and as a 40 mil (wet) film, whereas the remaining three
(3) Compositions B, C and D were all applied as 20 mil (wet) films.
All of the films were drawn on adhesive-backed polyester film under
a nitrogen blanket. The films were additionally allowed to dry
under the nitrogen blanket.
TABLE-US-00004 TABLE 4 ORDER OF WT. % COMPONENT ADDITION A B C D
Methanol 1 64.37 64.37 64.37 64.37 Deionized Water 2 32.88 32.88
32.88 32.88 Hydroxyethyl cellulose 3 1.31 -- 0.44 0.87 (Natrosol
250 HR CS) Hydroxypropyl cellulose 4 -- 1.31 0.87 0.44 (Klucel H
CS) SnCl.sub.2.cndot.2H.sub.2O 5 1.31 1.31 1.31 1.31 Indigo Carmine
6 0.13 0.13 0.13 0.13
Films A (both 20 and 40 wet mil thickness) and B were then exposed
to air at temperatures of 0.degree. F., 40.degree. F., or room
temperature (RT=72.+-.3.degree. F.). Films C and D were exposed to
air at 0.degree. F. and 40.degree. F.
Times at which color changes occurred from orange to blue for (wet)
film thickness of 20 and 40 mil, and temperatures of 0.degree. F.,
40.degree. F., and RT, are summarized in Table 5.
TABLE-US-00005 TABLE 5 Wet film thickness Time required for color
change (days) Composition A 0.degree. F. 40.degree. F. RT 20 mil
118 .+-. 7 56 .+-. 6 10 .+-. 5 40 mil 102 .+-. 8 96 .+-. 14 102
.+-. 8
The color progressions of films drawn from Composition B are
summarized in Table 6.
TABLE-US-00006 TABLE 6 Wet film thickness Time required for color
change (days) Composition B 0.degree. F. 40.degree. F. RT 20 mil 72
.+-. 11 20 .+-. 6 3 .+-. 2
The color progressions of films drawn from Composition C are
summarized in Table 7.
TABLE-US-00007 TABLE 7 Time required for color Wet film thickness
change (days) Composition C 0.degree. F. 40.degree. F. 20 mil 99
.+-. 8 28 .+-. 7
The color progressions of films drawn from Composition D are
summarized in Table 8.
TABLE-US-00008 TABLE 8 Time required for color Wet film thickness
change (days) Composition D 0.degree. F. 40.degree. F. 20 mil 79
.+-. 13 51 .+-. 6
* * * * *